Acoustic shock waves are used in medicine for various indications. It is known that tumors and bodily secretions, such as gallstones, can be destroyed by acoustic shock waves. It is also known that the formation of new bone tissue can be induced and promoted by shock waves. Finally, shock waves are also used for pain therapy.
In all these applications, the shock waves act on a target area inside the body. For this purpose it is necessary for the shock waves, which are generated outside the body, to pass through body tissue to arrive at the target area and be focussed on this area. Depending on the type of treatment, it is intended and desired that the shock waves act with a greater or lesser degree of effectiveness in the target area. The body tissue through which the shock waves pass on their way to the target area, however, should interact as little as possible with the shock waves, because such interaction can lead to undesirable damage to this body tissue.
So far, damage to the body tissue located outside the target area has been minimized essentially by focussing the shock waves. The shock waves passing through the body tissue outside the target area thus have a relatively low energy density, whereas the density of the shock waves in the target areas increased by focussing.